This invention relates to a flexible or floppy disk (which may be abbreviated to xe2x80x9cFDxe2x80x9d) for use in a removable type magnetic recording/reproducing device such as a flexible or floppy disk drive (which may be abbreviated to xe2x80x9cFDDxe2x80x9d).
As is well known in the art, the flexible disk of the type described comprises a magnetic recording medium and a jacket for receiving the magnetic recording medium. The magnetic recording medium comprises a flexible thin sheet composed of synthetic resin, a magnetic recording layer formed on a surface of the flexible thin sheet, and a coating layer formed on the magnetic recording layer.
On the other hand, the flexible disk drive of the type described is an apparatus for carrying out data recording and reproducing operation to and from the magnetic recording medium of the flexible disk inserted or loaded therein. In recent years, the flexible disks are more and more improved to have a larger storage capacity. Specifically, development is made of the flexible disks having the storage capacity of 128 megabytes (which may be called large-capacity FDs) In contrast with the flexible disks having storage capacity of 1 megabytes or 2 megabytes (which may be called small-capacity FDs). Following such development, the flexible disk drives have also been improved to accept the large-capacity FDs for data recording and reproducing operations to and from the magnetic recording media of the large-capacity FDs. Furthermore, the large-capacity FDs are more improved to have a larger storage capacity of 256 Mbytes, 512 Mbytes, . . . , and so on.
Throughout the present specification, flexible disk drives capable of recording/reproducing data for magnetic recording media of the large-capacity FDs alone will be referred to as xe2x80x9chigh-density exclusive type FDDs.xe2x80x9d On the other hand, flexible disk drives capable of recording/reproducing data for magnetic recording media of the small-capacity FDs alone will be called xe2x80x9clow-density exclusive type FDDs.xe2x80x9d Furthermore, flexible disk drives capable of recording/reproducing data for magnetic recording media of both the large-capacity and the small-capacity FDs will be called xe2x80x9chigh-density/low-density compatible type FDDs.xe2x80x9d In addition, the high-density exclusive type FDDs and the high-density/low-density compatible type FDDs will collectively be called xe2x80x9chigh-density type FDDS.xe2x80x9d
The low-density exclusive type FDD and the high-density type FDD are different in mechanism from each other in several respects, one of which will presently be described. In either FDD, a pair of magnetic heads is supported by a carriage which is driven by a drive arrangement to move in a predetermined radial direction with respect to the magnetic disk medium of the flexible disk loaded in the flexible disk drive. The difference resides in the structure of the structure of the drive arrangement. More specifically, the low-density exclusive type FDD uses a stepping motor as the drive arrangement. On the other hand, the high-density type FDD uses a linear motor such as a voice coil motor (which may be called xe2x80x9cVCMxe2x80x9d for short) as the drive arrangement.
Now, description will be made in slightly detail as regards the voice coil motor used as the drive arrangement in the high-density type FDD. The voice coil motor comprises a voice coil and a magnetic circuit. The voice coil is disposed on the carriage at a rear side and is wound around a drive axis extending in parallel to the predetermined radial direction. The magnetic circuit generates a magnetic field in a direction intersecting that of an electric current flowing through the voice coil. With this structure, by causing the electric current to flow through the voice coil in a direction intersecting that the magnetic field generated by the magnetic circuit, a drive force occurs in a direction extending to the axis on the basis of interaction of the electric current with the magnetic field. The drive force causes the voice coil motor to move the carriage in the predetermined radial direction.
Another difference between the low-density exclusive type FDD and the high-density type FDD resides in the number of revolution of a spindle motor for rotating the magnetic recording medium of the flexible disk loaded therein. More specifically, the low-density exclusive type FDD may rotate the magnetic recording medium of the small-capacity FD loaded therein at a low rotation speed having the number of revolution of either 300 or 360. On the other hand, the high-density type FDD can admit, as the flexible disk to be loaded therein, either the large-capacity FD alone or both of the large-capacity FD and the small-capacity FD. As a result, when the large-capacity FD is loaded in the high-density type FDD, the spindle motor for the high-density type FDD must rotate the magnetic recording medium of the large-capacity FD loaded therein at a high rotation speed having the number of revolution of 3,600 rpm which is equal to ten or twelve times as large as that of the small-capacity FD.
In the meanwhile, the large-capacity FD generally has an external configuration identical with that of the small-capacity FD. Specifically, both of the large-capacity and the small-capacity FDs have a flat rectangular shape of a width of 90 mm, a length of 94 mm, and a thickness of 3.3 mm in case of a 3.5-inch type. However, the large-capacity FD has a narrower track width (track pitch) than that of the small-capacity FD. As a result, it is difficult for the large-capacity FD to position a magnetic head of the high-density type FDD on a desired track in the magnetic recording medium thereof in contrast with the small-capacity FD. Accordingly, a servo signal for position detection is preliminarily written in the magnetic recording medium of the large-capacity FD.
In addition, the flexible disk is called a disk cartridge in the manner known in the art. The disk cartridge comprises the magnetic recording medium, upper and lower shells for receiving the magnetic recording medium with a space left therebetween, an upper liner adhered to an inner surface of the upper shell, and a lower liner adhered to an inner surface of the lower shell. The magnetic recorded medium is disposed between the upper and the lower liners. A combination of the upper and the lower shells is referred to as the jacket. That is, the magnetic recording medium is received in the jacket
The jacket is made by molding of synthetic resin. Specifically, the jacket comprises the combination of the upper and the lower shells each of which is generally made by injection molding.
The upper and the lower liners are for removing fine dust from adhered to upper and lower surfaces of the magnetic recording medium. Each of the upper and the lower liners is annular in shape and comprises a nonwoven fabric sheet which is made of, for example, rayon. The upper and the lower shells are provided with upper and lower rectangular head windows, respectively, to permit an access to the magnetic recording medium by a pair of magnetic heads.
The magnetic recording medium has an annular shape with a medium circular opening formed at its center to be concentric with a center axis of the magnetic recording medium. The magnetic recording medium is made of a magnetic material having a flexibility. That is, as described above, the magnetic recording medium comprises the flexible thin sheet composed of synthetic resin, the magnetic recording layer formed on the surface of the flexible thin sheet, and the coating layer formed on the magnetic recording layer. The magnetic recording medium is supported at the periphery of the medium circular opening by a metal hub through a double-sided adhesive tape called an A ring in the art.
The metal hub is generally made by press molding of a metal plate. Specifically, the metal hub has a substantially dish shape and comprises a concave portion at its center thereof and an outer circumferential portion at the periphery of the concave portion. That is, the concave portion consists of a cylindrical portion and a circular bottom portion. In addition, the outer circumferential portion is called a flange portion which is formed at the upper end of the cylindrical portion. The jacket or the lower shell has a shell circular opening or a jacket center circular hole serves to expose the concave portion of the metal hub to the exterior of the jacket. In addition, the metal hub serves to chuck the flexible disk at a disk holder table of the flexible disk drive. Specifically, the metal hub has a hub center hole formed at its center and a chucking hole formed at a position eccentric with the hub center hole. The disk holder table is rotatably driven by a spindle motor. The spindle motor comprises a spindle shaft to which the disk holder table is fixed at an upper portion thereof. The disk holder table is provided with a chucking pin formed thereon. The spindle shaft and the chucking pin are inserted to the hub center hole and the chucking hole to rotate the magnetic recording medium of the flexible disk in a predetermined rotation direction.
Inasmuch as the lower shell or the jacket has the jacket center circular hole, there is a gap between the metal hub and the jacket center circular hole. It is difficult to completely get rid of the gap from a point of view for preventing a collision between the metal hub and the jacket on relative rotation therebetween when the magnetic recording medium of the flexible disk is accessed by the magnetic heads. The gap is equal to about 1 mm.
With structure of the above-mentioned conventional flexible disk, a small amount of dust may intrude or invade in the jacket via the gap. In a special case where the flexible disk is the large-capacity FD, a rotating magnetic recording medium winds up the dust in the circumference in accordance with a similar principle in a tornade because the magnetic recording medium rotates at a very high rotation speed of 3600 rpm as mentioned before. That is, the large-capacity FD swallows up, in the jacket via the jacket center circular hole, not only dust near to the jacket center circular hole but also dust far from the jacket center circular hole by rotating the magnetic recording medium at the high rotation speed.
That is, the conventional flexible disk is disadvantageous in that a reading error and a writing error tends to occur due to presence of the dust intruded via the gap when the magnetic recording medium is accessed by the magnetic heads of the flexible disk drive.
In order to resolve this problem, Japanese Unexamined Patent Publication of Tokkai No. Hei 11-45,540 or JP-A 11-45540 discloses or provides a flexible disk which is capable of preventing dust from intruding in the jacket via the gap between the metal hub and the jacket center circular hole. In the manner which will later be described in conjunction with FIG. 4, the flexible disk according to JP-A 11-45540 comprises the lower liner which has an inner peripheral part extended to the gap between the metal hub and the jacket center circular hole. That is, the lower liner has a liner opening of a liner opening diameter which is smaller than a jacket opening diameter of the jacket center circular hole so as to bring the liner opening diameter near a cylindrical outer diameter of the metal hub as much as possible.
However, a free movement of the metal hub may be regulated if the inner peripheral part of the lower liner is too close to the cylindrical portion of the metal hub. This is because the lower liner is adhered to the inner surface of the lower shell. When the movement of the metal hub is regulated, a chucking error or the like tends to occur. As a result, it is difficult for the flexible disk according to JP-A 11-45540 to bring the inner peripheral part of the lower liner near the cylindrical portion of the metal hub.
It is therefore an object of the present invention to provide a flexible disk which is capable of preventing dust from intruding in a jacket without regulating a movement of a metal hub.
Other objects of this invention will become clear as the description proceeds.
On describing the gist of an aspect of this invention, it is possible to be understood that a flexible disk comprises a generally disk-shaped sheet-like magnetic recording medium, a jacket consisting of upper and lower shells for receiving the magnetic recording medium so that the magnetic recording medium is rotatable, and generally annular upper and lower liners attached to inner surfaces of the upper and the lower shells, respectively. The magnetic recording medium is provided with a rotation supporting metal hub attached to a center portion thereof. The lower shell is provided with a jacket center circular hole to expose the metal hub on the exterior of the jacket.
According to a first aspect of this invention, the above-mentioned lower liner has an inner peripheral part which is extended to a gap between the metal hub and the jacket center circular hole. The inner peripheral part has slits in a radial manner.
According to a second aspect of this invention, the above-understood flexible disk further comprises an annular auxiliary liner, freely mounted on the lower liner, for extending to a gap between the metal hub and the jacket center circular hole.
According to a third aspect of this invention, the above-understood flexible disk further comprises a member for substantially filling up a gap between the metal hub and the jacket center circular hole without regulating a movement of the metal hub.